CN1085194C - Process for producing acrylic acid - Google Patents
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- CN1085194C CN1085194C CN95115847A CN95115847A CN1085194C CN 1085194 C CN1085194 C CN 1085194C CN 95115847 A CN95115847 A CN 95115847A CN 95115847 A CN95115847 A CN 95115847A CN 1085194 C CN1085194 C CN 1085194C
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
- C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation
- C07C51/46—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation by azeotropic distillation
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Abstract
In a process for producing acrylic acid, wherein propylene and/or acrolein is catalytically oxidized with molecular oxygen in a vapor phase and the gas resulting from the oxidation is cooled and/or absorbed in water to form a crude aqueous acrylic acid, followed by azeotropic distillation to remove the water with an entrainer of a boiling point of no higher than 130 DEG C. on the crude aqueous acrylic acid which may have, upon necessity, undergone removal of aldehydes contained therein to produce acrylic acid purified in that the crude aqueous acrylic acid is substantially dehydrated, the improvement which comprises conducting the azeotropic distillation under such conditions that concentrations of the entrainer and water in the bottom product of the azeotropic distillation are from 5% to 30% by weight and no higher than 0.5% by weight, respectively, where the theoretical number of plates in the azeotropic distillation column for dehydration used and that in the distillation column for separating acetic acid used are preferably from 5 to 20. Highly-purified acrylic acid can thus be obtained from the crude aqueous acrylic acid without causing unfavorable polymerization of acrylic acid.
Description
The present invention relates to from the water-containing acrylic acid crude product, obtain the acrylic acid of purifying, and wherein avoided polymerizing acrylic acid.Particularly, the present invention relates to obtain highly purified acrylic acid by distillation, wherein avoided to have lower boiling impurity by the use entrainer, when from the water-containing acrylic acid crude product, removing as water and acetate, incidental polymerizing acrylic acid in the distillation tower, this water-containing acrylic acid crude product obtains from the catalyzed oxidation of the propylene that carries out with molecular oxygen gas phase and/or propenal.
The gas cooling that will obtain with the gas gas phase oxidation of propene and/or the propenal of molecule-containing keto in steam with oxide catalyst and/or absorb in water can obtain aqueous vinylformic acid crude product.This water-containing acrylic acid crude product not only contains vinylformic acid, and contains some by product such as acetate, formic acid, formaldehyde and acetaldehyde.When the transformation efficiency of oxidizing reaction hanged down, this water-containing acrylic acid crude product contained propenal a small amount of unconverted use or that form.In this case, propenal is removed from the water-containing acrylic acid crude product by using washing or similar approach, and the product that obtains obtains pure vinylformic acid through purifying.
Acrylic acid concentration in the water-containing acrylic acid crude product that obtains thus is 40% to 80% (weight).In by product, acetate most importantly contains the acetate of 1% to 5% (weight) in this water-containing acrylic acid crude product.To divide dried up, acetate and vinylformic acid from the water-containing acrylic acid crude product be not effectively by distilling directly, and reason is because their chemical similarity and physico-chemical property such as vapour-liquid equilibrium.As for the method that obtains pure acrylic acid, in recent years, people had proposed several method, comprised by using entrainer through component distillation dewater effectively step and the step by fractionation by distillation acetate.According to our classification, the method that has two types is in order to divide dried up and acetate, just, a kind of method that can be called " Dan Tafa ", wherein water and acetate are removed (Japanese patent specification 18967/1971 simultaneously by only using a distillation tower from vinylformic acid, 20372/1971,22456/1971,34692/1971 and 21124/1974, with Japanese Patent prospectus 246941/1993), method with a kind of being called " double tower method ", wherein dehydration and acetate separates by using two different distillation towers to carry out (Japanese patent laid-open publication gazette 15569/1966,18966/1971,25451/1975 and 10691/1988 respectively, Japanese Patent prospectus 181440/1991 and Japanese patent laid-open publication gazette 15495/1994 and 15496/1994).The present invention relates to the improvement of double tower method.
In preceding a kind of method, promptly in single tower method, only water and acetate are removed simultaneously with a tower.Therefore need to use distillation tower, also need high reflux ratio with many theoretical plate numbers.When use had stage number distillation tower how, the pressure of tower bottom therefore can be too high, so the temperature of bottoms is difficult to keep lower.Therefore it is disadvantageous using this distillation tower from the viewpoint of energy expenditure.Therefore in addition, vinylformic acid is to be easy to the polymeric material, and this is fatal shortcoming from the viewpoint of avoiding acroleic acid polymerization, because tower bottom reaches too high temperature.
In the double tower purification process, water is removed respectively from vinylformic acid by use two different distillation towers that design respectively for this reason with acetate.Therefore, can use respectively through tower optimization and that be suitable for dewatering and tower through optimizing and be suitable for separating acetic acid.Consider that from energy although use two towers, generally speaking this method is still favourable.And the acetate that reacts main by product as propylene and/or acrolein oxidation that is also advantageous in that of this double tower method can separate from the overhead product of separated from acetic acid distillation tower and reclaim.
The azeotropic distillation column that we are used to dewater to use carries out the distillatory condition with the distillation tower that is used for separating acetic acid to be studied, and above-mentioned two towers are used for being prepared into the double tower method of pure acrylic acid.In research process, we find that polymerization takes place vinylformic acid easily, particularly near the bottom of the azeotropic distillation column that is used to dewater.Therefore we have tested various distillation conditions so that eliminate following defective, promptly be used to the azeotropic distillation column that dewaters can not non-stop run for a long time because the polymerizing acrylic acid thing is in this distillation tower bottom deposition.Found that, can avoid in the incidental disadvantageous polymerizing acrylic acid of the azeotropic distillation column that is used for dewatering by being controlled at the water in the product of distillation tower bottom and the concentration of entrainer.The present invention is based on this discovery is accomplished.
The purpose of this invention is to provide a kind of commercial run for preparing pure acrylic acid, wherein in gas or gas phase with the gas of molecule-containing keto in the presence of steam flow with propylene and/or propenal catalyzed oxidation, the gas cooling that will from oxidation, obtain and/or in water, absorb or wash with water and form the water-containing acrylic acid crude product, this water-containing acrylic acid crude product dewaters through component distillation with entrainer by the azeotropic distillation column that use is used to dewater, and this dehydration carries out under improved condition so that the disadvantageous polymerizing acrylic acid of avoiding being caused in distillation tower.Another object of the present invention provides a kind of industrial advantageous method, the overhead product that wherein is used to the azeotropic distillation column that dewaters is divided into two-phase, promptly, be to contain water on the one hand, it contains all water and all or part acetate, this water and acetate contained in the water-containing acrylic acid crude product originally, be the entrainer phase on the other hand, all entrainers are returned to the azeotropic distillation column that is used to dewater with the backflow form, and contain water by again as washing water, the gas that is in the suds from oxidation stage is absorbed.
The present invention and embodiment preferred thereof are as follows:
1. in producing acrylic acid, wherein propylene and/or propenal are used the molecular oxygen catalysis oxidation in vapour phase, gas cooling that will obtain from oxidation stage and/or water absorb or wash with water and form the water-containing acrylic acid crude product, be not higher than 130 ℃ entrainer with boiling point then and remove the water that the water-containing acrylic acid crude product may exist through the component distillation that is used for dewatering, can remove wherein contained aldehyde as required to produce the vinylformic acid of purifying, wherein the vinylformic acid crude product is dehydrated in fact, and the improvement of carrying out is included in to be carried out component distillation and be respectively 5% to 30% (weight) and be no more than 0.5% (weight) to be used in the entrainer in the product of dehydration and azeotropic distillatory distillation tower bottom and the concentration of water under condition so.
2. according to the production acrylic acid of clause 1, wherein the concentration at the entrainer of the component distillation bottoms product that is used for dewatering is 6% to 15% (weight).
3. according to the production acrylic acid of clause 1 or 2, wherein the concentration at the water of the component distillation bottoms product that is used for dewatering is 0.05% to 0.3% (weight).
4. according to the production acrylic acid of one of clause 1 to 3, wherein in distillation tower, isolate lower boiling material as overhead product from the bottoms of the azeotropic distillation column that is used for dewatering, comprise acetate and entrainer, this tower is called the distillation tower of separating acetic acid hereinafter, obtain thus as the bottom product vinylformic acid that is used for the distillation tower of separating acetic acid, overhead product is returned to azeotropic distillation column.
5. according to the production acrylic acid of one of clause 1 to 4, wherein by component distillation, and the boiling point of entrainer is 80 ℃ to 130 ℃ to entrainer with water and acetate.
6. according to the production acrylic acid of one of clause 1 to 5, the temperature that wherein is used to the temperature of the component distillation tower bottom that dewaters and is used for the distillation tower bottom of separating acetic acid is not higher than 100 ℃.
7. according to the production acrylic acid of one of clause 1 to 6, the pressure that wherein is used to the component distillation top of tower that dewaters is 100 to 300mmHg, and the pressure that is used for the distillation tower top of separating acetic acid is 50 to 200mmHg.
8. according to the production acrylic acid of one of clause 1 to 7, wherein being used to azeotropic distillation column that dewaters and the theoretical plate number that is used for the distillation tower of separating acetic acid is respectively 5 to 20.
9. according to the production acrylic acid of one of clause 1 to 8, wherein charging contains vinylformic acid 40% to 80% (weight) in the water-containing acrylic acid crude product of the azeotropic distillation column that is used to dewater, acetate 1% to 5% (weight) and water 20% to 60% (weight).
10. according to the production acrylic acid of one of clause 1 to 9, in fact the overhead product that wherein is used to the azeotropic distillation column that dewaters contains all water and part or all of acetate, this water and acetate originally were included in the water-containing acrylic acid crude product, azeotrope is divided into two-phase, promptly, entrainer phase and water, all entrainers are circulated to the azeotropic distillation column that is used to dewater mutually and reflux, and part or all of water is reused for washing to absorb the gas that is produced by oxidizing reaction as water.
Therefore the present invention relates to the method for purifying water-containing acrylic acid crude product, this crude product is by the gas cooling that will obtain with molecular oxygen catalysis propylene oxide and/or propenal in vapour phase and/or wash with water and obtain.Has lower boiling impurity by using entrainer from the water-containing acrylic acid crude product, to remove, as water and acetate, suitably be controlled at the water of bottoms of the azeotropic distillation column that is used for dewatering and the concentration of entrainer, to avoid in distillation tower otherwise the polymerizing acrylic acid that can be initiated obtains highly purified vinylformic acid thereby produce.
According to the present invention, can stablize and operate continuously the distillation tower of azeotropic distillation column and separating acetic acid for a long time, obtain the applicable highly purified vinylformic acid of making the acrylate raw materials for production with can having the industrialization advantage.
The unique accompanying drawing of this paper is the schema of explanation embodiment of the present invention.
Produce the summary of purifying propenoic acid
In this produces acrylic acid, in vapour phase with molecular oxygen catalysis propylene oxide and/or methacrylaldehyde, the gas cooled that will from oxidation reaction, obtain and/or wash with water or in water, absorb and obtain the water-containing acrylic acid crude product. The water-containing acrylic acid crude product that forms thus not only contains acrylic acid, also has some by product such as acetic acid, formic acid, formaldehyde and acetaldehyde. When the transforming degree of oxidation reaction hangs down, contain a small amount of unconverted methacrylaldehyde in this water-containing acrylic acid crude product, therefore, if necessary, methacrylaldehyde is by using washing or similar approach to remove. Then water-containing acrylic acid crude product (in this manual, term " water-containing acrylic acid crude product " comprises that those process preliminary treatment are as removing the water-containing acrylic acid crude product of methacrylaldehyde) at least through the purification of dehydration, is obtained pure acrylic acid thus. Particularly, water-containing acrylic acid crude product process is being dewatered with the entrainer azeotropic distillation at the azeotrope tower that is used for dehydration, in fact all water, formic acid and formaldehyde, and part acetic acid is removed from the water-containing acrylic acid crude product as the overhead for the azeotrope tower that dewaters. Therefore, obtain containing the bottom product acrylic acid that originally is present in the acetic acid in the water-containing acrylic acid crude product as the remainder of impurity. Then this bottom product is processed in the destilling tower for separating of acetic acid, wherein acetic acid and entrainer are removed as distillate. The all or part distillate is circulated to above-mentioned azeotropic distillation for dehydration mutually, and treated to separate and to be recovered in the acrylic acid that contains in the distillate again. The bottom product that pure acrylic acid can be used as the destilling tower of separating acetic acid obtains. Pure acrylic acid is used as acrylic acid, or is used to next step esterification and obtains acrylate.
Acrylic acid is the raw material that is easy to polymerization. Therefore those skilled in the art knows that acrylic acid polymer produces in acrylic acid destilling tower of being everlasting, so that can not operate this tower again. We find after using following destilling tower continuously, and disadvantageous acrylic acid polymer results near the bottom for the azeotrope tower of dehydration easily, and near the top for separating of the destilling tower of acetic acid. Therefore, we change the condition of using these destilling towers to distill. Found that, be not less than respectively 5% (weight) by the concentration that is controlled at entrainer in the azeotropic distillation bottoms product and water but be not higher than 30% (weight); When not being higher than 0.5% (weight), can successfully avoid therefore can continuously operating these destilling towers for a long time in the azeotrope tower that is used for dehydration and disadvantageous acrylic acid polymerization that in for separating of the destilling tower of acetic acid, can be caused.
Processed gas
In industrial production acrylic acid, in vapour phase, mostly in the presence of air-flow, use gas catalysis propylene oxide and/or the methacrylaldehyde of molecule-containing keto, by the gas cooled that will produce in the oxidation, and/or wash with water or in water, absorb and obtain the water-containing acrylic acid crude product, wherein contain acrylic acid 40% to 80% (weight), acetic acid 1% to 5% (weight) and water 20% to 60% (weight). Important from the used water yield of absorption of gases of considering economically acrylic acid absorption/scrubbing tower, to carry out.
When the water yield that is used for absorption of gases increased, the concentration of acrylic acid in the water-containing acrylic acid crude product reduced. The load that consequently is used for the azeotrope tower of dehydration increases. Azeotropic dehydration
Consider that from avoiding the acroleic acid polymerization angle concentration height of entrainer in the bottom product of azeotrope tower is preferred. But, when this excessive concentration, what carry out for the destilling tower that dewaters, from the energy increase that needs for the azeotropic distillation bottoms product separation and azeotropic agent of dewatering. Therefore this excessive concentrations is disadvantageous economically. And, in this case, the acrylic acid end product can be polluted by entrainer, so entrainer can reduce acrylic acid purity and have high boiling material at those, such as polymerization inhibitor, from acrylic acid, be removed rear inhibition acroleic acid polymerization and generate water miscible polymer. Preferably on such level, namely it does not hinder the separation of the acetic acid that carries out to the concentration of the entrainer in bottom product in for separating of the destilling tower of acetic acid. But in fact the concentration of entrainer depends on that also can entrainer and acetic acid azeotropic distillation. Its result, the concentration of the entrainer in bottom product preferably are controlled at 5% (weight) to 30% (weight), usually in 6% to 15% (weight), more preferably in 6% to 13% (weight) scope. When the concentration of entrainer is inadequate, also can be to for separating of the entrainer that adds additional quantity in the destilling tower of acetic acid.
The present invention also requires to satisfy another condition. For other necessary condition of the operation of the azeotrope tower that satisfy to be used for dehydration, the concentration of water of bottom product that is used for the azeotrope tower of dehydration is controlled at 0.5% (weight) or still less. This can realize that its corresponding heat is provided by reboiler by the amount of entrainer phase that controlled circulation is back to for the azeotrope tower of dehydration. The concentration of the water in bottom product can reduce with the entrainer amount mutually that increases circulating reflux by the amount of vaporization that is increased in reboiler. In order to reach purpose of the present invention, that is: avoid acroleic acid polymerization, the concentration of the water in bottom product to be controlled at 0.5% (weight) or still less, preferred 0.3% to 0.05% (weight). Cross when low when the concentration of water, the bottom temp that is used for the azeotrope tower of dehydration raises, and this is disadvantageous to being avoided acroleic acid polymerization. And, when the concentration of water is crossed when low, need the more entrainer of circulating reflux to the azeotrope tower that is used for dehydration, its overhead can contain so many acetic acid amount so that only have a small amount of acetic acid to reclaim from the overhead for separating of the destilling tower of acetic acid. Preferably, to be back to the amount of entrainer for the azeotrope tower of dehydration be charging in 1 to 10 times of the weight of the water of the water-containing acrylic acid solution of azeotrope tower.
Except the condition of entrainer and water azeotropic distillation, importantly to have normal boiling point be 130 ℃ or lower to entrainer, the organic solvent that preferable range is 80 to 130 ℃. When the boiling point of entrainer was higher than 130 ℃, being separated in for separating of being difficult in the destilling tower of acetic acid between entrainer and the acrylic acid carried out. For this reason, entrainer is stayed in the bottom product easily, and the acrylic acid of purifying is polluted by entrainer. Therefore, acrylic acid purity reduces. On the other hand, when the boiling point of entrainer was lower than 80 ℃, the vacuum that is used for the azeotrope tower of dehydration can not improve, so the rising of the temperature at destilling tower top, caused the easier generation of acrylic acid polymerization.
The instantiation of entrainer comprises toluene, heptane, cyclohexane, hexahydrotoluene and isobutyl ether. These entrainers not only can with water can also with the acetic acid azeotropic distillation, so they have so that the segregative effect of acetic acid, above-mentioned separated from acetic acid is steamed tower and is carried out in for separating of the destilling tower of acetic acid at the azeotropic that is used for dehydration. Therefore these entrainers can be so that reflux ratio reduces; Low reflux ratio is favourable economically. Also can use not with acetic acid but with the organic solvent of water azeotropic distillation, for example, ro-butyl acetate, acetic acid isobutyl, isopropyl acetate and methyl iso-butyl ketone (MIBK). Thisly during as entrainer, do not need a large amount of entrainer of circulating reflux mutually to the azeotrope tower that is used for dehydration with the organic solvent of acetic acid azeotropic distillation when using, so as without any the method for other separating acetic acids the time effective separation acetic acid. Therefore this is disadvantageous for all overheads in the destilling tower that is cycled to used in separating acetic acid at the azeotrope tower that is used for dehydration. Preferably this overhead is introduced the step that reclaims acetic acid, separate and reclaim acetic acid with this. Above-mentioned entrainer can use separately or, natch, mix to use. The distillation of separating acetic acid
The azeotrope tower bottoms product that is used for dehydration that all moisture in the water-containing acrylic acid crude product have been removed is in fact told acetic acid through distillation from acrylic acid, wherein acrylic acid obtains as bottom product, and low boiling such as acetic acid and entrainer are removed from its top. Preferably will be not less than 50% the low boiling distillation that from the destilling tower for separating of acetic acid, steams and be circulated to azeotrope tower for dehydration.
Destilling tower can be conventional, and its prerequisite is that it has and reaches " theoretical tray " that the distilling effect that provides above requires. Distillation procedure
Be used for dehydration azeotrope tower bottom product temperature and preferably be not higher than 100 ℃ for separating of the temperature of acetic acid destilling tower bottom product. Preferably, the azeotrope tower that is used for dehydration is that 100 to 60 ℃ and top temperature are to operate under 30 to 60 ℃ the condition making its end temperature; Be that 100 to 60 ℃ and top temperature are to operate under 30 to 60 ℃ the condition for separating of the destilling tower of acetic acid making its end temperature. Usually use these destilling towers in decompression, so the temperature of its bottom product can be controlled by controlling respectively its top pressure. The top pressure that is used for the azeotrope tower of dehydration is controlled at 100 usually to 300mmHg, and it has 30 to 50 blocks of column plates usually when this destilling tower is plate column, and maybe this destilling tower has 5 to 20 column plates usually when representing with theoretical cam curve. Pressure for separating of the destilling tower top of acetic acid is controlled at 50 usually to 200mmHg, the destilling tower that uses has 15 to 50 blocks of plates usually, and (theoretical cam curve is usually: 5 to 20), (theoretical cam curve is preferred 30 to 40 blocks of plates usually: 10 to 15). This destilling tower is not limited to plate column, also can use packed column and any other destilling tower, and its prerequisite is that they have the theoretical cam curve that reaches described distilling effect requirement.
For separating of the destilling tower of acetic acid so that the acrylic acid that migrates out from the destilling tower bottom for separating of acetic acid is wherein acetic acid and the content of water is not higher than respectively 0.1% (weight) and is not higher than under pure acrylic acid condition of 0.1% (weight) and operate. For fear of disadvantageous acrylic acid polymerization, usual way is at the polymerization inhibitor that adding is arranged such as phenol or amine polymerization inhibitor, as, quinhydrones, Hydroquinone monomethylether or phenthazine distill under existing, and polymerization inhibitor is usually along with the solution of acrylic acid, entrainer and water adds from the destilling tower top. In addition, for identical purpose, the gas of molecule-containing keto is blown into the destilling tower from the bottom.
The overhead product of the azeotropic distillation column that is used to dewater is the aqueous solution, and it contains acetate and a small amount of formic acid and formaldehyde that all or part originally contained in the water-containing acrylic acid crude product.This aqueous solution is used effectively because when its sent back to above-mentioned to the washing process of vapor phase oxidation gas in the time be used as water and absorb vinylformic acid in the gas that contains other compositions.Contain at the aqueous solution under the situation of entrainer, if the aqueous solution is removed wherein entrainer through distillation in advance, cooling then can be circulated in the washing process then.When the entrainer that uses is a kind of like this hydrocarbon, promptly it is in fact insoluble in water, for example is toluene, and when heptane or hexanaphthene, this entrainer can be easily removed from the overhead distillate of the azeotropic distillation column that is used for dewatering by decant.
The acrylic acid concentration that preferably is used for the moisture distillate of the component distillation that dewaters is 1% (weight) or lower.When because the separation efficiency deficiency of the azeotropic distillation column that is used to dewater, when containing a large amount of vinylformic acid in the moisture distillate, can cause acrylic acid loss.But if moisture distillate is washed the vapor phase oxidation product as water again, the part acrylic acid that contains in moisture distillate can be recovered in wash tower bottoms.
Typical embodiment
Be usually directed to the schema shown in the accompanying drawing now typical embodiments of the present invention is described.But technical scope of the present invention is not limited to this schema and also is not limited to following explanation.
The gas that the gas catalysis propylene oxide and/or the propenal with molecule-containing keto that will carry out in the presence of steam flow in vapour phase produces passes through pipe 1 charging in the washing tower A of absorbing propenoic acid, and contacts with the water of introducing tower A by pipe 7, and vinylformic acid is absorbed in the entry.Therefore can obtain water-containing acrylic acid crude product as the bottoms of the tower A that is used for absorbing propenoic acid.Usually, in order to improve acrylic acid assimilation effect, will partly cool off and be recycled into absorbing propenoic acid among the tower A (not shown in the accompanying drawings) by the bottoms that pipe 2 is extracted out usually.The preferred overhead product that is used to the azeotropic distillation column B that dewaters comes absorbing propenoic acid as water, and this overhead product infeeds among the tower A by the pipe 7 that shows in the accompanying drawings, so that reduce the water yield of consumption as far as possible.Except vinylformic acid, can contain by product such as acetate, formic acid, formaldehyde and the propenal of oxidizing reaction in the water-containing acrylic acid crude product.Therefore, if necessary, can make the water-containing acrylic acid crude product enter propenal vaporization tower to remove propenal (not shown in the accompanying drawings) wherein.
The water-containing acrylic acid crude product of bottoms that will be used for the tower A of absorbing propenoic acid is introduced the azeotropic distillation column B that is used for dewatering by managing 2.By managing 5 entrainer introduced the azeotropic distillation column B be used to dewater, and carry out component distillation.The distillate that the steam of discharging from the top of distillation tower B by condensation obtains contains entrainer, water and all or part of acetate that has contained the water-containing acrylic acid crude product, when used entrainer is insoluble in water this distillate is separated or decant.Therefore the whole entrainers that reclaim return to distillation tower B backflow by managing 4.Water is drawn out of, and delivers to tower A and be reused for absorbing propenoic acid by managing 7.Also can the sucking-off of part water also be discharged so that the water yield in the equilibrium system by pipe 8.Especially, for the concentration of the water of controlling the azeotropic distillation column B bottoms that is used for dewatering, can control the amount of the entrainer phase that is sent back backflow.The amount of the entrainer of being sent back to depends on the azeotropic composition of water and entrainer.Therefore the concentration of the water in bottoms is controlled at 0.5% (weight) or lower, preferred 0.3% to 0.05% (weight); Entrainer concentration in bottoms is controlled at 5% to 30% (weight), preferred 6% to 15% (weight), more preferably 6% to 13% (weight).
Bottoms charging by managing the 6 azeotropic distillation column B that will be used to dewater is in the distillation tower C that is used for separating acetic acid.In this distillation tower C, all lower boiling impurity all are removed as overhead product basically, and pure vinylformic acid obtains as bottoms, and it can be extracted out by pipe 10.If desired, the vinylformic acid of purifying can be introduced next step (not showing in the accompanying drawings), for example, vinylformic acid is used as the raw material of acrylate there.
To mainly be made up of acetate, entrainer and vinylformic acid, the overhead product that obtains from the top of the distillation tower C that is used for separating acetic acid is sent azeotropic distillation column B and the circulation that is used to dewater back to by managing 9, so that the wherein contained vinylformic acid of recovery.On the other hand, the distillate charging in the step of separating and reclaim acetate (not showing in the accompanying drawings), is obtained pure acetate thus.Isolating vinylformic acid and entrainer also can return to the azeotropic distillation column B that is used for dewatering in this step.
The temperature of each distillation tower bottom product is controlled at 100 ℃ or lower.
Now be described more specifically the present invention by the following embodiment that mentions.
Embodiment 1
Carry out the dehydration distillation of water-containing acrylic acid by the RECTIFYING APPARATUS USED IN LABORATORY of using glass.In this water distilling apparatus, distillation column is to have the glass cylinder that diameter is 50mm, and 1 liter of flask as reboiler is housed in its bottom, at its top condenser is housed.The outlet of condenser connects a vacuum unit.Filling in the distillation column and highly be the 3mm Raschig tubes of 90cm.This highly corresponding theoretical plate number is 15.The distillate of the condenser condenses that will install in this column top is separated with decantor.After this, all entrainers are returned to this post mutually reflux, water is extracted out.The reboiler flask is heated in oil bath.Flask is immersed in the oil bath, add heat by the temperature regulation of controlling oil.By bottoms being extracted out from flask to keep the liquid level in the flask constant with a pump.
Water-containing acrylic acid as the distillation starting soln contains vinylformic acid 55% (weight), acetate 1.5% (weight), formaldehyde 0.3% (weight) and a small amount of formic acid.By using toluene, carry out the azeotropic dehydration distillation test as entrainer.With water-containing acrylic acid and toluene respectively with the feeding rate of 280g/ hour and 14ml/ hour from the by-level face feeding distillation column of distillation column.Regulate pressure to 180mmHg.To add from the column top as the quinhydrones and the thiodiphenylamine of polymerization retarder.Air is injected the flask that places the column bottom with 15ml/ hour input rate.The feed rate of polymerization retarder is controlled at the quinhydrones that makes in bottoms and the concentration of thiodiphenylamine is respectively 800ppm and 500ppm.
The component distillation post operate continuously that will be used to dewater 7 hours.Its column top temperature is 49 ℃, and the temperature of bottoms is 90 ℃, and the amount that returns to the entrainer phase that refluxes the column top is 830ml.When distillation flattens when steady the vinylformic acid gas chromatographic analysis that will extract out from the column bottom.Found that vinylformic acid contains the acetate of 2.3% (weight), the water of 0.5% (weight), the toluene of 7% (weight), and polymerization retarder.With vinylformic acid is to extract out from the column bottom in 170.5g/ hour with the mean rate.The aqueous phase that obtains as distillate from the column top finds to contain the acetate of 0.2% (weight), the vinylformic acid of 0.1% (weight), formaldehyde and formic acid.
After distillation flattened steady 7 hours, stop distillation, observe water distilling apparatus inside.Found that in as the flask of third generator and and all do not have acrylate copolymer on the weighting material surface of distillation column.Embodiment 2 to 4 and comparative example 1 to 3
According to embodiment 1 in identical mode carry out the azeotropic dehydration distillation test, its prerequisite is will and send the entrainer amount mutually that distillation column refluxes as the toluene amount of entrainer back to change so that the toluene concentration of change in bottoms.After distillation flattened steady 7 hours, stop test, water distilling apparatus is taken apart.Examine as the inside of the flask of reboiler and the weighting material of distillation column bottom, look at whether to have acrylate copolymer to generate.
With the composition of water in the bottoms and entrainer, the temperature of bottoms, the results are shown in Table 1 to above-mentioned observation that the water distilling apparatus of taking apart carries out.
Table 1
| Embodiment | The comparative example | |||||
| 2 | 3 | 4 | 1 | 2 | 3 | |
| Entrainer | Toluene | → | → | → | → | → |
| The bottoms temperature (℃) | 93 | 89 | 96 | 89 | 90.5 | 91 |
| Bottoms is formed water (weight %) entrainer (weight %) | 0.05 8.2 | 0.3 12.2 | 0.04 6.6 | 0.8 5.5 | 0.5 4.5 | 0.7 2.9 |
| To the weighting material in the flask post of the observations column bottom of water distilling apparatus | a a | a a | a a | b d | a e | c c |
A: do not find polymkeric substance.
Near b: liquid level, find polymer belt (wide 2mm, thick 0.3mm).
Liquid flooding takes place after c:5 hour; Can not continue test.
D: find about 50 particle/polymers (2-3mm ) than lower part at packing layer.
E: find about 20 particle/polymers (2-3mm ) on the weighting material surface.Embodiment 5 and 6 and comparative example 4 and 5
Except replacing toluene as the entrainer, repeat the method for embodiment 1 to 4 with methyl iso-butyl ketone (MIBK) or isopropyl acetate.Obtain that the results are shown in Table 2.
Table 2
A, b and d: see Table 1f: find about 100 Mi Huazhuanjuhewus (2-3mm ) in the packing layer bottom
| Embodiment | The comparative example | |||
| 5 | 6 | 4 | 5 | |
| Entrainer | Methyl iso-butyl ketone (MIBK) | Isopropyl acetate | Methyl iso-butyl ketone (MIBK) | Isopropyl acetate |
| Column head pressure (mmHg) | 170 | 200 | 170 | 200 |
| The bottoms temperature (℃) | 96 | 93 | 90 | 100 |
| Bottoms is formed water (weight %) entrainer (weight %) | 0.1 5.5 | 0.3 7.6 | 0.9 0.23 | 0.1 2.4 |
| To the weighting material in the flask post of the observations column bottom of water distilling apparatus | a a | a a | f f | b d |
Claims (18)
1. produce acrylic acid for one kind, wherein propylene and/or propenal are used the molecular oxygen catalysis oxidation in vapour phase, the gas cooling that will from oxidation stage, obtain and/or in water, absorb or wash with water and form the water-containing acrylic acid crude product, be not higher than 130 ℃ entrainer with boiling point then and remove the water that the water-containing acrylic acid crude product may exist through the component distillation that is used for dewatering, can remove wherein contained aldehyde as required to produce the vinylformic acid of purifying, wherein the water-containing acrylic acid crude product is dehydrated in fact, and the improvement of carrying out is included in to be carried out component distillation and be respectively 5% to 30% (weight) and be no more than 0.5% (weight) to be used in the entrainer in the product of dehydration and azeotropic distillatory distillation tower bottom and the concentration of water under condition so.
2. according to the production acrylic acid of claim 1, wherein the concentration at the entrainer of the component distillation bottoms product that is used for dewatering is 6% to 15% (weight).
3. according to the production acrylic acid of claim 1 or 2, wherein the concentration at the water of the component distillation bottoms product that is used for dewatering is 0.05% to 0.3% (weight).
4. according to the production acrylic acid of one of claim 1 to 2, wherein in distillation tower, isolate lower boiling material as overhead product from the bottoms of the azeotropic distillation column that is used for dewatering, comprise acetate and entrainer, this tower is called the distillation tower of separating acetic acid hereinafter, obtain thus as the bottom product vinylformic acid that is used for the distillation tower of separating acetic acid, overhead product is returned to azeotropic distillation column.
5. according to the production acrylic acid of one of claim 1 to 2, wherein by component distillation, and the boiling point of entrainer is 80 ℃ to 130 ℃ to entrainer with water and acetate.
6. according to the production acrylic acid of one of claim 1 to 2, the temperature that wherein is used to the temperature of the component distillation tower bottom that dewaters and is used for the distillation tower bottom of separating acetic acid is not higher than 100 ℃.
7. according to the production acrylic acid of one of claim 1 to 2, the pressure that wherein is used to the component distillation top of tower that dewaters is 100 to 300mmHg, and the pressure that is used for the distillation tower top of separating acetic acid is 50 to 200mmHg.
8. according to the production acrylic acid of one of claim 1 to 2, wherein being used to azeotropic distillation column that dewaters and the theoretical plate number that is used for the distillation tower of separating acetic acid all is respectively 5 to 20.
9. according to the production acrylic acid of one of claim 1 to 2, wherein charging contains vinylformic acid 40% to 80% (weight) in the water-containing acrylic acid crude product of the azeotropic distillation column that is used to dewater, acetate 1% to 5% (weight) and water 20% to 60% (weight).
10. according to the production acrylic acid of one of claim 1 to 2, in fact the overhead product that wherein is used to the azeotropic distillation column that dewaters contains all water and part or all of acetate, this water and acetate originally were included in the water-containing acrylic acid crude product, azeotrope is divided into two-phase, promptly, entrainer phase and water, all entrainers are circulated to the azeotropic distillation column that is used to dewater mutually and reflux, and part or all of water is reused for washing to absorb the gas that is produced by oxidizing reaction as water.
11. according to the production acrylic acid of one of claim 1 to 2, wherein entrainer is that boiling point is a kind of solvent of 80-130 ℃ at least, it is selected from aliphatic hydrocarbon and aromatic hydrocarbon and isobutyl ether, and with water and acetate component distillation.
12. according to the production acrylic acid of one of claim 1 to 2, wherein entrainer is that a kind of boiling point is 80-130 ℃ a solvent at least, it is selected from alkyl acetate and methyl iso-butyl ketone (MIBK) and gasifies with the water azeotropic.
13. according to the production acrylic acid of one of claim 1 to 2, the amount that wherein is back to the entrainer of the azeotropic distillation column that is used for dewatering is charging in 1 to 10 times of the weight of the water of the water-containing acrylic acid solution of azeotropic distillation column.
14. according to the production acrylic acid of one of claim 1 to 2, wherein being used to the azeotropic distillation column that dewaters is that 100 to 60 ℃ and top temperature are to operate under 30 to 60 ℃ the condition making its end temperature.
15. according to the production acrylic acid of one of claim 1 to 2, the distillation tower that wherein is used for separating acetic acid is that 100 to 60 ℃ and top temperature are to operate under 30 to 60 ℃ the condition making its end temperature.
16., wherein be used for the azeotropic distillation column that dewaters and be respectively 6% to 15% (weight) and be no more than under the condition of 0.3% (weight) in the concentration that makes its bottoms entrainer and water and operate according to the production acrylic acid of one of claim 1 to 2.
17., wherein will be not less than the lower boiling distillment that 50% the distillation tower from being used for separating acetic acid steams and be circulated to the azeotropic distillation column that is used for dewatering according to the production acrylic acid of one of claim 1 to 2.
18. according to the production acrylic acid of one of claim 1 to 2, the distillation tower that wherein is used for separating acetic acid is making that the vinylformic acid that migrates out from the distillation tower bottom that is used for separating acetic acid is that wherein the acetate and the content of water is respectively under the pure acrylic acid condition that is not higher than 0.1% (weight) and is not higher than 0.1% (weight) and operates.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20152294A JP3937462B2 (en) | 1994-08-04 | 1994-08-04 | Acrylic acid purification method |
| JP201522/94 | 1994-08-04 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1129692A CN1129692A (en) | 1996-08-28 |
| CN1085194C true CN1085194C (en) | 2002-05-22 |
Family
ID=16442447
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN95115847A Expired - Lifetime CN1085194C (en) | 1994-08-04 | 1995-08-04 | Process for producing acrylic acid |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5910607A (en) |
| EP (1) | EP0695736B1 (en) |
| JP (1) | JP3937462B2 (en) |
| CN (1) | CN1085194C (en) |
| DE (1) | DE69509451T2 (en) |
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| JP6907516B2 (en) * | 2015-12-25 | 2021-07-21 | 三菱ケミカル株式会社 | (Meta) Acrylic acid manufacturing method |
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- 1995-08-04 DE DE69509451T patent/DE69509451T2/en not_active Expired - Lifetime
- 1995-08-04 EP EP95112302A patent/EP0695736B1/en not_active Expired - Lifetime
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| GB2146636A (en) * | 1983-08-11 | 1985-04-24 | Nippon Catalytic Chem Ind | Process for producing acrylic acid |
Also Published As
| Publication number | Publication date |
|---|---|
| DE69509451T2 (en) | 1999-10-07 |
| EP0695736A1 (en) | 1996-02-07 |
| JP3937462B2 (en) | 2007-06-27 |
| US5910607A (en) | 1999-06-08 |
| CN1129692A (en) | 1996-08-28 |
| EP0695736B1 (en) | 1999-05-06 |
| DE69509451D1 (en) | 1999-06-10 |
| JPH0840974A (en) | 1996-02-13 |
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